U.S. patent number 10,790,907 [Application Number 16/856,753] was granted by the patent office on 2020-09-29 for optical transmitter, optical receiver and optical link.
This patent grant is currently assigned to KONINKLIJKE PHILIPS N.V.. The grantee listed for this patent is KONINKLIJKE PHILIPS N.V.. Invention is credited to Gerhardus Wilhelmus Lucassen, Martinus Bernardus Van Der Mark, Klaas Cornelis Jan Wijbrans.
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United States Patent |
10,790,907 |
Wijbrans , et al. |
September 29, 2020 |
Optical transmitter, optical receiver and optical link
Abstract
The present invention relates to an optical link, comprising an
optical converter circuit (16) having an optoelectronic device (18)
and circuitry (20) connected to the optoelectronic device (18). The
optoelectronic device (18) has a plurality of individual
optoelectronic segments (18a-18i). The optical link further
comprises an elongated optical guide (14) having a single optical
fiber optically connected at a first end to the optoelectronic
device (18) and configured to transmit light away from the
optoelectronic device (18), wherein the individual optoelectronic
segments (18a-18i) have different positions relative to the first
end of the optical fiber so that light beams emitted by the
optoelectronic segments (18a-18i) are coupled into the optical
fiber under different angles. The optoelectronic device (18) is
configured to receive from the circuitry (20) on at least some of
the segments (18a-18i) a plurality of data streams and optically
send the plurality of data streams as spatially diverse data
streams into the optical guide (14). The optical link further
comprises a photo detector arrangement (28) optically connected to
a second end of the optical guide (14) and having a plurality of
photo detector segments (28a-28i) arranged to optically receive the
plurality of data streams from the optoelectronic device (18), and
a processing unit (30) associated with the photo detector
arrangement (28) and configured to extract the plurality of data
streams from the photo detector arrangement (28).
Inventors: |
Wijbrans; Klaas Cornelis Jan
(Rijen, NL), Lucassen; Gerhardus Wilhelmus
(Eindhoven, NL), Van Der Mark; Martinus Bernardus
(Best, NL) |
Applicant: |
Name |
City |
State |
Country |
Type |
KONINKLIJKE PHILIPS N.V. |
Eindhoven |
N/A |
NL |
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Assignee: |
KONINKLIJKE PHILIPS N.V.
(Eindhoven, NL)
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Family
ID: |
1000005084607 |
Appl.
No.: |
16/856,753 |
Filed: |
April 23, 2020 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20200259565 A1 |
Aug 13, 2020 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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16307958 |
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10659164 |
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PCT/EP2017/064855 |
Jun 17, 2017 |
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Foreign Application Priority Data
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Jun 23, 2016 [EP] |
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16175971 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04B
10/2581 (20130101); H04B 10/502 (20130101); H04B
10/69 (20130101); H04B 10/40 (20130101); H04J
14/04 (20130101); H04B 10/516 (20130101) |
Current International
Class: |
H04B
10/40 (20130101); H04J 14/04 (20060101); H04B
10/50 (20130101); H04B 10/69 (20130101); H04B
10/516 (20130101); H04B 10/2581 (20130101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Sakaguchi, J. et al "19-Core Fiber Transmission of 19x100x172-Gb/s
SDM-WDM-PDM-QPSK signals at 305Tb/s", Optical Fiber Communication
Conference and Exposition Mar. 2012. cited by applicant .
Sleiffer, V.A., et al "Mode-Division-Multiplexed 3x112-Gb/s DP-QPSK
Transmission over 80-km few-mode fiber with inline MM-EDFA and
Blind DSP", 38th European Conference and Exhibition on Optical
Communnications Sep. 2012. cited by applicant .
Ryf, Roland et al "Mode-Division Multiplexing over 96 km of
Few-Mode Fiber using Coherent 6 x 6 MIMO Processing", Journal of
Lightwave Technology, IEEE Service Center, vol. 30, No. 4, Feb.
2012, pp. 521-531. cited by applicant .
Haydaroglu, Iskender et al "Optical Power Delivery and Data
Transmission in a Wireless and Batteryless Microsystem using a
Single Light Emitting Diode", Journal of Microelectromechanical
Systems, vol. 24, No. 1 Feb. 2015. cited by applicant .
Van Der Mark, Martin B. et al "All-optical power and data transfer
in catheters using an efficient LED", Proc. of SPIE vol. 9317,
2015. cited by applicant .
Grin lens: www.grintech.de, 2018. cited by applicant.
|
Primary Examiner: Ismail; Omar S
Parent Case Text
CROSS-REFERENCE TO PRIOR APPLICATIONS
This application is a continuation of U.S. patent application Ser.
No. 16/307,958, filed Dec. 7, 2018, which is the U.S. National
Phase application under 35 U.S.C. .sctn. 371 of International
Application No. PCT/EP2017/064855, filed on Jun. 17, 2017, which
claims the benefit of European Patent Application No. 16175971.7,
filed on Jun. 23, 2016. These applications are hereby incorporated
by reference herein.
Claims
The invention claimed is:
1. An optical transmitter, comprising: an optical converter circuit
having an optoelectronic device and circuitry connected to the
optoelectronic device, the optoelectronic device having a plurality
of individual optoelectronic segments; an elongated optical guide
having a single optical fiber optically connected at a first end to
the optoelectronic device and configured to transmit light away
from the optoelectronic device, wherein the plurality of individual
optoelectronic segments have different positions relative to the
first end of the single optical fiber so that light beams emitted
by the plurality of individual optoelectronic segments are coupled
into the optical fiber under different angles, the optoelectronic
device being configured to receive from the circuitry on at least
some of the plurality of individual optoelectronic segments, a
plurality of data streams and optically send, via the light beams
emitted by the at least some of the plurality of individual
optoelectronic segments, the plurality of data streams as spatially
diverse data streams into the optical guide, further comprising a
gradient index (GRIN) lens arranged between the optoelectronic
device and the optical guide for optically coupling the light
emitted from the optoelectronic device into the optical guide.
2. The optical transmitter of claim 1, wherein the optoelectronic
device is further configured to receive optical energy through the
optical guide and convert the optical energy into electrical
energy.
3. The optical transmitter of claim 1, wherein the at least some of
the plurality of individual optoelectronic segments of the
optoelectronic device to which the separate data streams are input
have different center wavelengths of light emission.
4. The optical transmitter of claim 1, wherein at least some of the
plurality of individual optoelectronic segments of the
optoelectronic device are connected in series.
5. The optical transmitter of claim 1, wherein the optoelectronic
device is a light emitting diode segmented into a plurality of
light diode segments forming the plurality of individual
optoelectronic segments.
6. The optical transmitter of claim 1, wherein the plurality of
individual optoelectronic segments are single light emitting
diodes.
Description
FIELD OF THE INVENTION
The present invention relates to optical transmitters, optical
receivers and optical links and methods of operating optical links.
An optical link may be used for optically supplying energy to a
remote electronic device, and/or for data transmission to and from
a remote electronic device.
BACKGROUND OF THE INVENTION
An optical link having an optical transmitter and an optical
receiver is useful in applications, where power delivery and/or
data transmission via electrical wires is problematic, in
particular due to size restrictions of the power delivery and/or
data transmission paths. Although the present invention is not
limited to a use in medical applications, the present invention
will be described herein with respect to medical applications.
There is a clear and ongoing trend to replace conventional surgical
procedures with minimally invasive interventions. Reduced trauma,
shorter hospital stay and reduced costs are the most important
drivers of the adoption of minimally invasive techniques. To enable
further innovation in medical instrumentation--thus enabling more
advanced and more challenging minimally invasive
interventions--there is a need to integrate miniature sensors for
in-body imaging and physiological measurement in instruments like
catheters and guide wires.
Data and power delivery to the tip of long and thin devices such as
a medical catheter or guide wire for imaging, sensing, sensitizing
or even ablation can be challenging. Including, on top of that, a
high data rate return channel from the distal to the proximal end
is even more problematic. This is due to several reasons.
Firstly, the combination of the small cross-section (i.e. small
diameter), necessary for the medical intervention, combined with
the long length of a guide wire or catheter does severely limit the
total number of electrical wires that can be integrated in such an
instrument.
Secondly, the integration of multiple electrical wires compromises
the flexibility of the instrument, while flexibility is a key
property of this type of instruments.
Thirdly, for high data rate, such as e.g. required for an
ultrasound transducer at the tip or for sensitive measurements, one
often requires coaxial cables which need even more space compared
to single-core wires.
Fourthly, instruments with electrical wires typically are not
compatible with the use of magnetic resonance imaging due to
resonances in/of the electric wiring leading to electromagnetic
interference in the connected electronics and also possibly leading
to tissue heating. And furthermore, thin electrical cables
typically cannot support a relatively high amount of power for use
at the distal end of the catheter.
Also, because of their disposable use, catheters and guide wires
must be manufactured in a relatively simple and cost-effective
way.
Sakaguchi et al.: "19-core fiber transmission of
19.times.100.times.172-Gb/s SDM-WDM-PDM-QPSK signals at 305 Tb/s",
Optical Fiber Communication Conference and Exposition, 2012 and the
National Fiber Optical Engineers Conference, IEE, 4 Mar. 2012,
pages 1-3, report on a free-space coupling system combined with a
multi-core fiber enabling upscaling to a record
space-division-multiplexed channel number of 19.
Sleiffer et al.: "Mode-division-multiplexed 3.times.112-Gb/s
DP-QPSK transmission over 80-km few-mode fiber with inline MM-EDFA
and Blind DSP", 2012, 38th European Conference and Exhibition on
Optical Communications, 16 Sep. 2012, pages 1-3 describe
transmission of a 3.times.112-GB/s DP-QPSK
mode-division-multiplexed signal up to 80 km, with and without
multi-mode EDFA, using blind 6.times.6 MIMO digital signal
processing.
Roland Ryf et al.; "Mode-Division Multiplexing Over 96 km of
Few-Mode Fiber Using Coherent 6.times.6 MIMO Processing", Journal
of Lightwave Technology, IEEE Service Center, New York, US, vol.
30, no. 4, 1 Feb. 2012, pages 521-531 describe simultaneous
transmission of six spatial and polarization modes, each carrying
40 Gb/s quadrature-phase-shift-key channels over 96 km of a
low-differential group delay few-mode fiber. U.S. Pat. No.
5,963,349A discloses an optical wavelength-division multiplexed
bidirectional data link using a single multi-mode fiber.
WO 2014/072891 A1 describes an optical link comprising an optical
guide through which optical energy is transmitted to a remote
distal optoelectronic converter having an optoelectronic device in
form of a light emitting diode (LED) which converts the optical
energy into electrical energy for powering the optical converter
circuit and one or more electronic devices. On the one hand, this
known optical link is effective in providing sufficient power
delivery capability to actuate an ultrasound catheter, because the
optoelectronic device has a large surface area necessary to achieve
the necessary power output. On the other hand, the large surface
area of the optoelectronic device limits the bandwidth and, hence,
the data rate of data transmission. For this reason, it is further
proposed there to use a separate optoelectronic device for data
transmission in the return path from the distal end to the proximal
end. However, a separate optoelectronic device for data
transmission and a separate optoelectronic device for energy
harvesting add significant complexity to both the electronic and
optical part of the interventional instrument using the optical
link.
Therefore, there is a need for an improved optical transmitter,
optical receiver and optical link which retains the capability of
achieving sufficient power output, but increases the bandwidth and
data rate in the return path.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an optical
transmitter and an optical receiver which are capable of
transmitting data with high data rate, while maintaining the
capability to achieve a power output sufficient for powering one or
more electronic devices.
In a first aspect of the present invention, an optical transmitter
is provided, comprising:
an optical converter circuit having an optoelectronic device and
circuitry connected to the optoelectronic device, the
optoelectronic device having a plurality of individual
optoelectronic segments,
an elongated optical guide having a single optical fiber optically
connected at a first end to the optoelectronic device and
configured to transmit light away from the optoelectronic device,
wherein the individual optoelectronic segments have different
positions relative to the first end of the optical fiber so that
light beams emitted by the optoelectronic segments are coupled into
the optical fiber under different angles,
the optoelectronic device being configured to receive from the
circuitry on at least some of the segments a plurality of data
streams and optically send, via the light beams emitted by the at
least some of the segments, the plurality of data streams as
spatially diverse data streams into the optical guide.
The optical transmitter according to the present invention thus
uses an optoelectronic device having a plurality of individual
optoelectronic segments. The individual optoelectronic segments may
be segments of a single segmented light emitting diode (LED), or
may be single LEDs forming together the optoelectronic device.
Using an optoelectronic device having a plurality of individual
optoelectronic segments has several advantages. A large-surface
area optoelectronic device has a high capacitance which in turn
limits the bandwidth and, hence, the data rate. When using an
optoelectronic device having a plurality of individual segments,
each of the segments has a reduced surface area and, thus, a
reduced capacitance. Thus, a single segment of the optoelectronic
device can transmit data with larger bandwidth and higher data
rate.
According to the invention, at least some of the segments of the
optoelectronic device are used for data transmission in the return
path from the optoelectronic device to a receiver. Each of these
segments thus forms a single data transmission channel. Thereby, it
is possible to increase the data rate by space-division
multiplexing. As described herein, the optoelectronic device is
particularly suitable for space-division multiplexing by spatially
modulating a plurality of separate data streams onto at least some
or all of the segments. In this case, each of the at least some or
each of all the segments can send an optical signal modulated with
a respective data stream under a different angle into the optical
fiber of the optical guide for transmitting the data streams. Such
an angle diversity is maintained in the optical fiber over at least
a few meters so that the single data streams can be distinguished
on a receiver.
The optoelectronic device is configured to send the plurality of
data streams as spatially diverse data streams. The plurality of
data streams may be spatially modulated onto the segments of the
optoelectronic device, and the segments then send the data streams
through the optical guide, e.g. the optical fiber, to a receiver.
Thus, space-division multiplexing may be achieved similar to the
techniques used in WiFi 802.11n/802.11ac standards using spatial
multiplexing.
The plurality of data streams may come from a plurality of
different data sources, e.g. from a plurality of measuring devices,
or from a single data source after having been split into the
plurality of data streams.
The optical guide of the optical transmitter according to the
present invention has an optical fiber which may be a single-core
or a multiple-core optical fiber. In case of a single-core optical
fiber, the optical fiber preferably is a multimode optical
fiber.
Using an optoelectronic device having a plurality of individual
segments has a further advantage of being less complex and more
cost-effective in comparison with separate optical converters for
energy harvesting and data transmission as proposed in the prior
art discussed above. An optoelectronic device having a plurality of
individual optoelectronic segments namely can be used for data
transmission with high rate and for energy harvesting.
In particular, as provided in a preferred embodiment, if at least
some of the segments of the optoelectronic device are connected in
series, a high electrical power output can be obtained sufficient
for powering one or more electronic devices and/or the optical
converter circuit.
The optical transmitter according to the invention may be
configured such that at least some of the segments of the
optoelectronic device are used for energy harvesting, i.e. for
converting optical energy into electrical energy, while at least
some other or the at least some same of the segments are used for
data transmission in the return path. Even here, the advantage of
large bandwidth and high data rate is obtained due to the reduced
surface area of the single segments.
Thus, the optoelectronic device is further preferably configured to
receive optical energy through the optical guide and convert the
optical energy into electrical energy.
In this embodiment, the optical transmitter according to the
invention provides at the same time an optical output with high
data rate and power continuity for supplying the electronic
converter circuit and/or other electronic devices with sufficient
electrical energy.
There is another benefit of the afore-mentioned embodiment,
according to which the optoelectronic device is configured to
harvest energy from incoming light and to transmit data in the
return path. In particular, if photo-induced electroluminescence is
used, energy can be received and data transmitted back at the same
time.
A further advantage of the afore-mentioned embodiment is that the
segments of the optoelectronic device may be used for differential
signaling in the return path. Differential signaling means
modulating a segment according to a first modulation and modulating
one or more other segments, which send(s) (its) their light under
different angle(s) into the optical guide, with a second modulation
which is the reverse of the first modulation. The advantage is a
more constant total power consumption of the optoelectronic device
and a more robust demodulation at the photo detector arrangement
side.
Further preferably, the circuitry of the optical converter circuit
has a data stream splitter configured to split a single original
data stream into a plurality of separate data streams, wherein each
of the separate data streams is input to one of at least some of
the segments, and wherein the circuitry further preferably has
modulators at an output of the data beam splitter and at an input
of at least some of the segments, the modulators being configured
to modulate, in particular spatially modulate the separate data
streams onto the at least some of the segments of the
optoelectronic device.
In this way, a single original data stream is broken down into
multiple single data streams which then can be modulated onto the
segments of the optoelectronic device. The modulators modulate the
single data streams broken down from the original continuous data
stream onto the single segments, thus enabling spatial modulation
of the separate data streams onto the optoelectronic device.
Further advantageously, the data stream splitter may be further
configured to add a preamble to each of the separate data streams
for enabling recognition of the spatially diverse data streams when
received by a receiver.
In this embodiment, at least some or all of the segments of the
optoelectronic device send data streams using a preamble that is
recognizable. At a receiver having a photo detector arrangement
having a plurality of photo detector segments, which will be
described later, a correlation may be performed between the
plurality of photo detector segments against the preambles so that
the maximum signal is achieved for each preamble as well as
suppression of the signals of the other photo detector segments.
This will give the different data streams that need to be
recognized. The same correlation is then used when the actual data
is being sent to reconstruct the data stream of a specific segment.
Thus, multiplexing may be based on segments sending their light
under different angles and then reconstructing those from the photo
detector segments, as the angle under which the light is sent
changes only a little or not over the length of the fiber.
In a further embodiment, the at least some of the segments of the
optoelectronic device of the transmitter to which the separate data
streams are input have different center wavelengths of light
emission. This embodiment enables wavelength-based multiplexing on
the optoelectronic device side and wavelength-based demultiplexing
at the receiver side. Wavelength multiplexing/demultiplexing may
thus preferably be combined with the previously mentioned
space-division multiplexing.
As already mentioned above, at least some of the optoelectronic
segments are preferably connected in series. Further preferably,
all of the optoelectronic segments are connected in series. A
series connection of the optoelectronic segments has the advantage
of providing a high voltage output when converting incoming optical
energy into electrical energy.
Further preferably, the optoelectronic device is a light emitting
diode segmented into a plurality of light diode segments. In this
embodiment, an LED may be split into a plurality of single
micro-LEDs with each micro-LED having a reduced surface area in
comparison with a conventional LED. Using a segmented LED is highly
cost-effective for use in the present invention. It is also
possible the optoelectronic device is formed by a plurality of
single optoelectronic devices, e.g. a plurality of single LEDs
arranged at different positions with respect to the light entrance
end of the optical fiber.
The optical transmitter according to the invention further
preferably comprises a gradient index (GRIN) lens arranged between
the optoelectronic device and the optical guide for optically
coupling the light emitted from the optoelectronic device into the
optical guide, and vice versa.
The GRIN lens advantageously collimates the light propagating
through the optical guide onto the optoelectronic device, thereby
ensuring even power distribution to at least some or all of the
segments of the optoelectronic device, which is useful for high
voltage output, when the optical transmitter is also used for
energy harvesting. Further, the GRIN lens couples the light emitted
by the optoelectronic device into the optical guide for data
transmission. In particular, when the optical guide is a single
core fiber, the GRIN lens projects the light emitted by the
optoelectronic device into the fiber core. The GRIN lens preferably
has a high numerical aperture (NA), for example higher than 0.2, or
higher than 0.3, or higher than 0.4, or higher than 0.5, or higher
than 0.6, or higher than 0.7. Further, the numerical aperture of
the light entrance/output end of the optical guide adjacent to the
GRIN lens may be matched to the numerical aperture of the GRIN
lens. It is to be understood that while a GRIN lens is preferred
because it enables a small and robust implementation, the optical
fiber of the optical guide may be coupled with the optoelectronic
device by a conventional lens or even without a lens by precise
positioning the optical fiber with respect to the optoelectronic
device.
In a second aspect of the invention, an optical receiver is
provided, comprising:
a photo detector arrangement having a plurality of photo detector
segments arranged to optically receive a plurality of light beams
propagating under different propagation angles and carrying a
plurality of data streams from an optical guide, and
a processing unit associated with the photo detector arrangement
and configured to extract the plurality of data streams from the
photo detector arrangement.
The photo detector arrangement of the optical receiver according to
the invention has a plurality of photo detector segments configured
to optically receive data streams, in particular as sent by the
optoelectronic device of the optical transmitter according to the
invention. The processing unit of the optical receiver according to
the invention is configured to extract the data stream or data
streams from the photo detector arrangement for further
analysis.
In case that a plurality of data streams are received by the photo
detector arrangement, the processing unit is further preferably
configured to combine the plurality of extracted data streams into
a single data stream, thus the processing unit is configured to
demultiplex the data streams extracted from the photo detector
arrangement.
The processing unit is preferably configured to extract the data
streams from the photo detector arrangement by using maximum ratio
combining across the photo detector segments.
Maximum ratio combining is a common technique to combine multiple
received data streams into a single continuous data stream and can
be advantageously used in the present invention to extract the
separate data streams from the plurality of photo detectors and to
combine them into a single high rate data stream.
In a third aspect of the invention, an optical link is provided,
comprising an optical transmitter according to the first aspect and
an optical receiver according to the second aspect.
According to a fourth aspect, an optical console is provided,
comprising an optical receiver according to the second aspect
The optical console according to the invention preferably comprises
a light source configured to emit a light beam for transmission
through the optical guide to the optoelectronic device of the
transmitter. Such a light source may be a VCSEL (Vertical Cavity
Surface Emitting Laser), or any other light source suitable for
emitting light with high optical energy. The light emission of the
light source may also be modulated to transmit control data through
the optical guide to the converter circuit and/or one or more
electronic devices for controlling same. If no energy harvesting
and no control data transmission is needed, the light source can be
omitted.
In a fifth aspect of the present invention, an optical probe is
provided, comprising an optical transmitter according to the first
aspect, wherein the optical converter circuit is integrated in a
distal end portion of the optical probe. Preferably, a proximal end
of the optical probe is connectable to the photo detector
arrangement of the receiver according to the second aspect.
The optical probe is for example a catheter or guidewire.
The advantages of the optical transmitter according to the
invention also apply to the optical probe according to the
invention. The optical probe has similar and/or identical preferred
embodiments as the optical transmitter according to the
invention.
In a sixth aspect of the present invention, a method of operating
an optical link is provided, comprising:
providing an optical converter circuit having an optoelectronic
device and circuitry connected to the optoelectronic device, the
optoelectronic device having a plurality of individual
optoelectronic segments,
supplying a plurality of data streams to at least some of the
segments and optically sending the plurality of data streams as
spatially diverse data streams by emitting light from at least some
of the optoelectronic segments under different angles into a single
fiber of an optical guide,
receiving through the optical guide on a photo detector arrangement
having a plurality of photo detectors the plurality of data streams
from the optoelectronic device, and
extracting the plurality of data streams from the photo detector
arrangement.
It will be understood that the claimed method has similar and/or
identical preferred embodiments as the claimed optical link as
described above and as defined in the dependent claims.
In a seventh aspect of the present invention, a computer program is
provided, comprising program code means for causing a computer to
carry out the steps of the method according to the sixth aspect,
when said computer program is carried out on a computer.
It shall be understood that the claimed method has similar and/or
identical preferred embodiments as the claimed devices and as
defined in the dependent claims.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other aspects of the invention will be apparent from and
elucidated with reference to the embodiment(s) described
hereinafter. In the following drawings
FIG. 1 shows a schematic embodiment of an optical transmitter, an
optical receiver, an optical link, an optical probe and a console
according to the present invention, and
FIG. 2 shows an embodiment of a detail of the optical transmitter
in FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an optical link labeled with general reference numeral
10 which comprises an optical transmitter 11 and an optical
receiver 15. Further shown in FIG. 1 is a console 13, which may
comprise the receiver 15 and a light source 12.
The light source 12 is capable of emitting light having an optical
energy. The light source 12 preferably is a VCSEL. The light
emitted by the VCSEL may be modulated in order to transmit control
data. The light of the light source may also be used for energy
harvesting as will be explained later. In case that control data
transmission and energy harvesting is not needed, the light source
can be omitted.
The optical link 10 further comprises an optical guide 14 which has
a single optical fiber. The optical fiber may be a single-core
multimode optical fiber, but also a multiple-core optical fiber. At
least a part of the optical guide 14 is part of the optical
transmitter 11.
The optical transmitter 11 further comprises an optical converter
circuit 16. The optical converter circuit 16 comprises an
optoelectronic device 18 and circuitry 20. The circuitry 20 may
comprise electronics 22, e.g. for power extraction and control data
extraction from the optoelectronic device 18. The electronics 22 is
electrically connected to the optoelectronic device 18,
accordingly. The circuitry 20 further comprises a data stream
splitter 24 and one or more modulators 26 between the output of the
data stream splitter 24 and the input of the optoelectronic device
18. The modulators 26 are electrically connected with the data
stream splitter 24 and with the optoelectronic device 18,
accordingly.
The optical receiver 15 comprises a photo detector arrangement 28
configured to detect light and convert the light into electrical
signals. A processing unit 30 which is electrically connected to
the photo detector arrangement 28 comprises one or more
demodulators 32 and a data stream combiner 34.
The optical link 10 further comprises an optical beam splitter 36
which may be configured as dichroic mirror. The optical beam
splitter 36 is arranged in the light path of the optical guide 14
between the light source 12 and the optoelectronic device 18 on the
one hand, and between the optoelectronic device 18 and the photo
detector arrangement 28, on the other hand. Again, if energy
harvesting and control data transmission is not needed, the beam
splitter 36 can be omitted, and the photo detector arrangement 28
can be arranged at a position, where the light source 12 is
positioned in FIG. 1.
The optical transmitter 10 may further comprise a first GRIN lens
38 arranged between a first end 40 of the optical guide 14 and the
optoelectronic device 18. The GRIN lens 38 preferably has a high
NA, in particular an NA>0.3.
The optical receiver 10 may have a second GRIN lens 42 arranged
between a second end 44 of the optical guide 14 and the photo
detector arrangement 28. The GRIN lens 42 has a high NA, which may
be >0.2.
The optoelectronic device 18 has a plurality of individual
optoelectronic segments 18a to 18i which are labeled with letters a
to i in FIG. 1. In particular, the optoelectronic device 18 is a
segmented light emitting diode (LED), wherein the segments 18a to
18i each form a single micro-LED, wherein each of the LED segments
18a to 18i may be configured to convert light into electrical
signals, and to convert electrical signals into light. In other
words, each of the segments 18a to 18i functions as an LED by
itself. In other embodiments, the optoelectronic device 18 may
comprise a plurality of single LEDs, each LED forming a segment of
the optoelectronic device 18. It is to be understood that the
converter circuit 16 may comprise multiple electronic circuits to
drive each of the segments 18a to 18i. An example of an electronic
circuit for one segment is shown in FIG. 2 described later.
A subset or number of the segments 18a to 18i or all segments 18a
to 18i may be connected in series with one another.
The optical transmitter 11, in particular the optoelectronic device
18 and the circuitry 20 can be integrated into an optical probe 46
which may be a catheter or guide wire or any other interventional
instrument. In particular, the optical converter circuit 16 may be
integrated in a distal tip portion 48 of the optical probe 46. The
optical probe 46 may have one or more additional electronic devices
(not shown), for example an ultrasound transducer, a camera, a
measuring device, in the distal tip portion 48. These devices
typically provide data streams which are to be sent by the
transmitter 11 to the receiver 15, as will be described later in
more detail. The GRIN lens 38 and a part of the optical guide 14
from the GRIN lens 38 up to the optical beam splitter 36 may also
be integrated into the optical probe 46 in a portion 50 of the
optical probe 46 which extends from the distal tip portion 48.
In the following, the optical link 10 and a method of operating
same will be further described.
One function of the optical link 10 may be power supply in that
light is transmitted from the light source 12 to the optical
converter circuit 16, wherein the optoelectronic device 18 of the
transmitter 11 converts optical energy transferred by the light
into electrical energy, for powering the components of the optical
converter circuit 16, and/or for powering any other electronic
device in the distal tip portion 48 of the probe 46. In FIG. 1, the
light emitted from the light source 12 is illustrated with arrows
52. This light is guided through the optical guide 14 through the
optical beam splitter 36 and further through the optical guide 14
and then passes through the GRIN lens 38. The GRIN lens 38
collimates the light from the light source 12 onto some or all of
the segments 18a to 18i of the optoelectronic device 18. Each of
the segments 18a to 18i or at least some of the segments 18a to 18i
convert the optical energy into electrical energy which may be
stored in a capacitor (not shown) of the electronics 22 for further
use as power supply to any of the components of the optical
converter circuit 16 or other device(s) in the distal portion of
the probe 46. In particular, when the segments 18a to 18i are
connected in series, or at least some of the segments 18a to 18i
are connected in series, the output voltage after conversion of the
optical energy into electrical energy can be high. A high voltage
is advantageous for specific ultrasound use of the probe 46. If a
III/V LED is used as a single segment of the optoelectronic device,
a single segment provides enough voltage for electronics, e.g. of
the converter circuit 16.
When using the optoelectronic device 18 as an energy converter, or
in other words as photovoltaic cell, the wavelength of the light
emitted by the light source 12 should be shorter than the central
wavelength of the light emission of the segments 18a to 18i of the
optoelectronic device 18.
A further function of the optical link 10 may be control data
transmission through the optical guide 14 to the optical converter
circuit 16 and/or other electronic devices in the distal tip
portion 48. To this end, the light emission of the light source 12
may be modulated with control data which are transmitted by the
light emitted from the light source 12 to the optoelectronic device
18, and after conversion of the modulated light into electrical
signals, the control data can be extracted by the electronics 22.
The control data transmitted in this way can be used for
controlling the optical converter circuit 16, and/or for
controlling one or more electronic devices in the distal tip
portion 48 as mentioned above.
A further and advantageous function of the optical link 10, in
particular the optical transmitter 11, is to optically transmit
data from the distal tip portion 48 of the optical probe 46 through
the optical guide 14. Due to the configuration of the
optoelectronic device 18 of the transmitter 11 with a plurality of
individual segments 18a-18i, the optoelectronic device 18 is
particularly suited to optically send data in the reverse
direction, also denoted as "in the return path", i.e. from the
optoelectronic device 18 through the optical guide 14 to the photo
detector arrangement 28 of the receiver 15. In particular, due to
the configuration of the optoelectronic device 18 having a
plurality of individual segments, the optoelectronic device 18 is
particularly suited to send multiple spatially diverse data
streams, as will be described hereinafter. Furthermore, the
configuration of the optoelectronic device 18 as a plurality of
small surface area segments has the advantage that the capacitance
of each of the segments 18a to 18i is lowered in comparison with a
large surface area optoelectronic device. Low capacitance enables
larger bandwidth and higher data rate in data transmission.
A single data stream is input to the data stream splitter 24 as
illustrated by an arrow 54. The incoming data stream may, for
example, come from an electronic device in the distal tip portion
48 of the probe 46, for example from an ultrasound transducer for
capturing ultrasound images, from a camera, etc. The data stream
splitter 24 splits the incoming data stream into a plurality of
separate data streams, in other words breaks down the incoming data
stream into a plurality of separate data streams. The separate data
streams are then input to the modulators 26 for spatially
modulating the separate data streams onto the segments 18a to 18i
of the optoelectronic device 18. At least some or all of the
segments 18a to 18i are used for data transmission in the return
path, and, thus, at least some or all of the segments 18a to 18i
are connected to a corresponding modulator 26.
The single segments 18a to 18i of the optoelectronic device 18 have
different positions with respect to the adjacent end of the optical
fiber of the optical guide 14. This means that the segments 18a to
18i emit their respective light beam carrying a data stream under
different angles into the optical fiber. Each segment 18a to 18i
may emit its light into the optical fiber at an angle which is
different from all other angles of light emission of the other
segments 18a to 18i. However, it is also possible that a first
subset of the segments 18a to 18i emits light into the fiber at the
same angle. In this case the segments of this subset are preferably
used for sending a single data stream. Another subset emitting
light into the fiber at a different angle than the first subset is
used for sending another data stream. By spatially multiplexing the
data streams, data rate is significantly increased.
The modulators 26 input the separate data streams to at least some
or all of the segments 18a to 18i of the optoelectronic device 18
depending on which of the segments 18a to 18i are used for data
transmission in the return path.
Due to the configuration of the optoelectronic device 18 having
multiple segments 18a to 18i, which can be configured as a matrix
or array arrangement of the segments 18a to 18i, the separate data
streams coming from the modulators 26 may be spatially modulated
onto the segments 18a to 18i or the corresponding subset of
segments as mentioned before.
Thus, the optoelectronic device 18 described herein enables
spaced-division multiplexing of the data streams which in turn may
be based on a single original continuous data stream. However, it
is also conceivable that the separate data streams may come from a
plurality of different data sources, e.g. from a plurality of
electronic devices.
FIG. 2 shows an embodiment of an electronic circuit for a segment
18a of the optoelectronic device 18. As mentioned before, each of
the segments 18a to 18i forms a micro-LED itself. FIG. 2 shows a
circuit in which the modulator 26 modulates the light emission
(arrow 56) with data. The modulation of the light emission of a
segment of the optoelectronic device 18 may be performed by
pinching the load of the segment. Light emission of the segment
may, for example, consist in a double flash for the data bit "0"
and a single flash for the data bit "1". In practice, a more simple
modulation scheme can be used, wherein a decrease of the amount of
light emitted by the segment denotes a `0`, and an increase of the
light emitted by the segment denotes a `1`, or vice versa, which
allows for higher data rates. Further, some kind of `whitening`
scheme can be employed by modifying the data such that there will
be no long sequences of `0` or `1` bits but instead a balanced load
over time.
The segments 18a to 18i or a subset of the segments 18a to 18i
optically send the spatially multiplexed data streams through the
GRIN lens 38 into the optical guide 14, as illustrated with arrows
58. The light signals of different segments 18a to 18i enter the
GRIN lens 38 and the optical guide 14, in particular the core of
the optical fiber, under different angles, i.e. with an angle
diversity, so that the separate data streams are transmitted as
spatially multiplexed data streams through the optical guide 14. At
the optical beam splitter 36, the light carrying the data streams
is directed to the photo detector arrangement 28.
The photo detector arrangement 28 has a plurality of photo detector
segments 28a to 28i labeled with letters a to i in FIG. 1, wherein
the number of photo detector segments of the photo detector
arrangement 28 may be the same as the number of segments 18a to 18i
of the optoelectronic device 18. The GRIN lens 42 uniformly
collimates the optical signals coming from the segments 18a to 18i
of the optoelectronic device 18 onto the photo detector segments
28a to 28i of the photo detector arrangement 28. In principle, all
segments 28a to 28i are used for receiving the optical signals from
the optoelectronic device 18. When sending light under a specific
angle through the optical guide 14, this corresponds to a specific
mode. Different modes have different delays in the fiber and there
will be some leakage to higher and lower order modes. By
correlating the received signals, one can reconstruct the
individual mode delays and thus advantageously combine the signals
from all photo detector segments 28a to 28i to have the best
reconstruction of the original signal. This can be further
improved, if the concept of differential signaling is applied which
will be explained farther below.
The photo detector segments 28a to 28i of the photo detector
arrangement 28 optically receive the optical light beams with the
spatially multiplexed data streams sent from the optoelectronic
device 18 and convert the optical signals into electrical
signals.
Like the segments 18a to 18i of the optoelectronic device 18, the
photo detector segments 28a to 28i of the photo detector
arrangement 28 may be arranged in a matrix or array.
When the optical signals are received by the photo detector
arrangement 28, the spatial multiplexing is still maintained,
because the optical signals emitted by the segments 18a to 18i of
the optoelectronic device 18 maintain their different propagation
angles up to the photo detector arrangement 28.
For enabling recognition of the received spatially diverse data
streams at the photo detector arrangement 28, i.e. the segments 28a
to 28i thereof, the data stream splitter 24 not only splits the
incoming data stream into separate data streams, but also adds a
preamble to each of the separate data streams. Several options are
possible here. One option is to use different pseudo-random
preambles for the individual data streams. Another option is to
multiplex in time and use the same preamble at each channel
individually. After learning the channel characteristics from the
preamble, these characteristics are used for the duration of a data
transmission (a packet) to decode the actual data.
The processing unit 30 uses these preambles when extracting the
separate data streams from the photo detector signals from the
single photo detector segments 28a to 28i. This can be
advantageously done by the technique of maximum ratio combining
which uses the preambles of each data stream. A correlation is
performed between the photo detectors 28a to 28i against the
preambles so that the maximum signal is achieved for each preamble
as well as the suppression of the signals of the other segments 28a
to 28i of the photo detector arrangement 28. The correlation can be
a simple correlation at one moment in time, but could also be a
correlation taking time delays into account and searching for the
time delay which gives the highest correlation.
The demodulators 32 then demodulate the extracted data streams from
the photo detector signals, and the data stream combiner 34
combines, i.e. demultiplexes the separate data streams into a
single continuous data stream. This combined data stream is then
output according to an arrow 60 for further processing, for example
for visualization of an image based on this data stream.
In addition to the spatial multiplexing of the data streams and
spatially multiplexed transmission of the data streams from the
optoelectronic device 18 to the photo detector arrangement 28, it
can also be envisaged to multiplex the data streams output from the
data stream splitter based on wavelength. To this end, the single
segments 18a to 18i of the optoelectronic device 18 may have center
wavelengths of light emission which vary over the segment array or
matrix.
Further, one of the major advantages of the optical link 10 is that
energy harvesting and data transmission by the optoelectronic
device 18 can be carried out simultaneously, i.e. optical energy
can be continuously converted into electrical energy, and at the
same time, multiple spatial data streams can be transmitted back
from the optoelectronic device.
Further, in this regard, the optical link 10 is advantageously
configured to use photo-induced electroluminescence.
In case of photo-induced electroluminescence, the light received by
the optoelectronic device 18 from the light source 12, may be
modulated to send information which is received by the segments 18a
to 18i as a common mode signal which can be extracted from the
harvested energy.
In general, photo-induced electroluminescence (PEL) is a type of
luminescence, which occurs, when an LED is illuminated with light
while its leads are connected to a resistance that is high enough
for the LED to build up a voltage higher than the band gap of the
LED. As a consequence, the LED will start to conduct and emit
light, as it does in conventional electroluminescence. Thus, light
entering the LED induces voltage in the LED, the voltage induces
current through the LED, the current induces light emission by the
LED. In case of efficient LEDs, this provides strong light emission
without a current source and variation of the load of the LED will
modulate the PEL output level.
Further in this regard, at least some or all of the segments 18a to
18i of the optoelectronic device 18 in connection with their
ability of energy harvesting at the same time may be used for
differential signaling in the return path. This will be explained
in the following.
For a single LED, by modulating the load on the illuminated LED,
PEL is generated, wherein the LED returns light at a different
wavelength than the incoming light received by the LED. The amount
of light that is returned is dependent on the load on the LED: If
less current is drawn, the voltage goes up and the LED emits more
light. Variation of the load changes the amount of light emitted by
the LED. However, it may be desirable to keep the total load
constant for the device. This can be achieved with the
optoelectronic device 18 having a plurality of segments 18a to 18i
by differential signaling.
The optoelectronic device 18 has multiple segments 18a to 18i. The
segments 18a to 18i are used for energy harvesting and signaling in
the return path simultaneously. At a certain power consumption, a
segment is in a certain working point which is a certain load on
the segment (e.g., 50% load). Normally, when sending a signal for a
single data transmission channel, the amount of light emitted by
the segment would be increased for the value `1` and decreased for
a value `0` in the binary case. With PEL this may be done by
changing the load on the individual segment. Thus, when sending a
signal, power consumption is being increased when sending a `1` and
being decreased when sending a `0`. Since the individual segments
18a to 18i are not correlated with one another, there can be large
variations in the total power consumption if coincidentally all
channels send a `1` or a `0` at the same time.
With differential signaling, some of the segments 18a to 18i are
modulated in a correlated manner such that the total power
consumption remains constant. In case of a simple binary modulation
(sending `0`s and `1`s), this means for example that two of the
segments 18a to 18i are modulated in anti-phase, i.e. if the one is
modulated with `1`, the other is modulated with `0`, and vice
versa.
As an example: Considering for example the segments 18a, 18b, 18c,
18d, each emitting its light beam into the optical fiber of the
optical guide 14 at a different angle, and each forming an
individual data transmission channel (C1, C2, C3, C4). According to
differential signaling, if a `1` is transmitted on channel C3, for
example, also a `0` is transmitted on channel C4, thus C3 and C4
transmit in anti-phase, resulting in the total power consumption
remains the same, and a further advantage is that the data streams
are sent under different angles and in anti-phase leading to a more
robust demodulation at the detector arrangement 28. Further, if a
`1` is transmitted on channel C2, a `0` is transmitted on channel
C1, etc. Because the segments are modulated as pairs in anti-phase,
the total load remains constant over all segments, because one
segment which is loaded less is compensated by another segment
loaded more.
In the optical fiber of the optical guide 14, this results in an
increase of the amount of light under one angle and a decrease of
the amount of light under another angle. This also leads to a more
robust transmission of the data streams, because one can "look for"
an increase of light in one channel and a decrease of light in
another channel to reliably detect a `1` and a `0` in the detector
arrangement 28. In total, the differential signaling disclosed
herein improves both the ability to have a constant power
consumption at a constant load as well as the robustness of the
data transmission in the return path.
While an example of the differential signaling has been given above
for the simple case of binary modulation, where two of the segments
18a to 18i are paired and modulated in anti-phase, the concept of
differential signaling can also be employed in case of multilevel
modulation. As an example with reference to the example above:
Sending a `1` on channel C3 (segment 18c) with 100% output (50%
load), and bringing the output of segments 18b (channel C2) and 18d
(channel C4) from 50% to 25% and in each case (2*-25%=-50% load),
could be done in multilevel modulation. Again, constant load is
obtained along with an increase of robustness of data transmission
by correlating across multiple channels here. This enables
spreading the signal over multiple channels to increase
robustness.
While the invention has been illustrated and described in detail in
the drawings and foregoing description, such illustration and
description are to be considered illustrative or exemplary and not
restrictive; the invention is not limited to the disclosed
embodiments. Other variations to the disclosed embodiments can be
understood and effected by those skilled in the art in practicing
the claimed invention, from a study of the drawings, the
disclosure, and the appended claims.
In the claims, the word "comprising" does not exclude other
elements or steps, and the indefinite article "a" or "an" does not
exclude a plurality. A single element or other unit may fulfill the
functions of several items recited in the claims. The mere fact
that certain measures are recited in mutually different dependent
claims does not indicate that a combination of these measures
cannot be used to advantage.
A computer program may be stored/distributed on a suitable medium,
such as an optical storage medium or a solid-state medium supplied
together with or as part of other hardware, but may also be
distributed in other forms, such as via the Internet or other wired
or wireless telecommunication systems.
Any reference signs in the claims should not be construed as
limiting the scope.
* * * * *
References